Readily-extractable hydroxyaluminium interlayers in clay- and silt-sized vermiculite

The dominant source of oxalate-soluble Al in the B horizon of a brown podzolic soil developed on andesite appears to be hydroxyaluminium interlayers in a dioctahedral vermiculite in the clay and silt fractions, of which the latter contributes most to the total extractable Al and fluoride reactivity of the whole soil. Cold sodium carbonate solutions extract as much interlayer Al as does oxalate, indicating that this fraction of the interlayer material is highly reactive, and sharply distinguished from more resistant interlayers which are also present.